A number of processes exist in the prior art for production of trimethylaluminum, but each of these processes suffers from the disadvantage in that each yields by-products which are of little or no value and thus present disposal problems. U.S. Pat. No. 2,744,127 describes a relatively simple process for the preparation of trimethylaluminum which produces as a by-product magnesium chloride in the weight ratio 2.7:1 magnesium chloride: trimethylaluminum. The magnesium chloride has little or no commercial value.
Several processes have been developed by which trimethylaluminum is prepared by the sodium reduction of methylaluminum sesquichloride as described in British Patent No. 762,200 and U.S. Pat. No. 2,954,389 and in an article by A. V. Grosse and J. M. Mavity, Journal of Organic Chemistry 5, 106 (1940). Preparation of trimethylaluminum has also been carried out by the sodium reduction of dimethylaluminum chloride as described in an article by S. Pasynkiewicz and M. Boleslawski, Journal of Organometallic Chemistry, 25, 29 (1970). The methods described in the above articles each form a basis for existing commercial processes for the production of trimethylaluminum, but each produce non-useable by-products having limited value in vast quantities in comparison to the trimethylaluminum produced. The by-products produced by the above processes are aluminum and sodium chloride.
The several processes that have utilized the above sodium reduction reactions suffer from an inherent problem in that trimethylaluminum will itself react with sodium to produce sodium tetramethylaluminate, a compound that, unless it reacts with dimethylaluminum chloride, will cause reduced yields and present a a disposal problem. Sodium tetramethylaluminate is extremely reactive towards moisture in the air, as would excess unreacted sodium. The disposal problems presented by these two compounds would represent a significant proportion of the cost of production of trimethylaluminum manufactured by those processes.
Although the conversion of dimethylaluminum chloride to trimethylaluminum without the use of sodium (Cryolite Process) is described in U.S. Pat. No. 2,839,556, this reaction scheme produces a vast amount of solid by-product having limited commercial value.
Two other methods for production of aluminum trialkyls are described in an article by R. Koster and P. Binger, Advances in Inorganic and Radiochemistry, I 1263 (1965) and by K. S. Pitzer and H. S. Gutowsky, Journal of American Chemical Society, 68, 2204 (1946). Both of these methods suffer from the use of expensive starting materials and the production of non-useful or extremely reactive by-products requiring expensive process equipment and handling techniques.